/*
 * (C) Copyright 2002 Linus Torvalds
 * Portions based on the vdso-randomization code from exec-shield:
 * Copyright(C) 2005-2006, Red Hat, Inc., Ingo Molnar
 *
 * This file contains the needed initializations to support sysenter.
 */

#include <linux/init.h>
#include <linux/smp.h>
#include <linux/thread_info.h>
#include <linux/sched.h>
#include <linux/gfp.h>
#include <linux/string.h>
#include <linux/elf.h>
#include <linux/mm.h>
#include <linux/err.h>
#include <linux/module.h>

#include <asm/cpufeature.h>
#include <asm/msr.h>
#include <asm/pgtable.h>
#include <asm/unistd.h>
#include <asm/elf.h>
#include <asm/tlbflush.h>
#include <asm/vdso.h>
#include <asm/proto.h>

enum {
        VDSO_DISABLED = 0,
        VDSO_ENABLED = 1,
        VDSO_COMPAT = 2,
};

#ifdef CONFIG_COMPAT_VDSO
#define VDSO_DEFAULT    VDSO_COMPAT
#else
#define VDSO_DEFAULT    VDSO_ENABLED
#endif

#ifdef CONFIG_X86_64
#define vdso_enabled                    sysctl_vsyscall32
#define arch_setup_additional_pages     syscall32_setup_pages
#endif

/*
 * This is the difference between the prelinked addresses in the vDSO images
 * and the VDSO_HIGH_BASE address where CONFIG_COMPAT_VDSO places the vDSO
 * in the user address space.
 */
#define VDSO_ADDR_ADJUST        (VDSO_HIGH_BASE - (unsigned long)VDSO32_PRELINK)

/*
 * Should the kernel map a VDSO page into processes and pass its
 * address down to glibc upon exec()?
 */
unsigned int __read_mostly vdso_enabled = VDSO_DEFAULT;

static int __init vdso_setup(char *s)
{
        vdso_enabled = simple_strtoul(s, NULL, 0);

        return 1;
}

/*
 * For consistency, the argument vdso32=[012] affects the 32-bit vDSO
 * behavior on both 64-bit and 32-bit kernels.
 * On 32-bit kernels, vdso=[012] means the same thing.
 */
__setup("vdso32=", vdso_setup);

#ifdef CONFIG_X86_32
__setup_param("vdso=", vdso32_setup, vdso_setup, 0);

EXPORT_SYMBOL_GPL(vdso_enabled);
#endif

static __init void reloc_symtab(Elf32_Ehdr *ehdr,
                                unsigned offset, unsigned size)
{
        Elf32_Sym *sym = (void *)ehdr + offset;
        unsigned nsym = size / sizeof(*sym);
        unsigned i;

        for(i = 0; i < nsym; i++, sym++) {
                if (sym->st_shndx == SHN_UNDEF ||
                    sym->st_shndx == SHN_ABS)
                        continue;  /* skip */

                if (sym->st_shndx > SHN_LORESERVE) {
                        printk(KERN_INFO "VDSO: unexpected st_shndx %x\n",
                               sym->st_shndx);
                        continue;
                }

                switch(ELF_ST_TYPE(sym->st_info)) {
                case STT_OBJECT:
                case STT_FUNC:
                case STT_SECTION:
                case STT_FILE:
                        sym->st_value += VDSO_ADDR_ADJUST;
                }
        }
}

static __init void reloc_dyn(Elf32_Ehdr *ehdr, unsigned offset)
{
        Elf32_Dyn *dyn = (void *)ehdr + offset;

        for(; dyn->d_tag != DT_NULL; dyn++)
                switch(dyn->d_tag) {
                case DT_PLTGOT:
                case DT_HASH:
                case DT_STRTAB:
                case DT_SYMTAB:
                case DT_RELA:
                case DT_INIT:
                case DT_FINI:
                case DT_REL:
                case DT_DEBUG:
                case DT_JMPREL:
                case DT_VERSYM:
                case DT_VERDEF:
                case DT_VERNEED:
                case DT_ADDRRNGLO ... DT_ADDRRNGHI:
                        /* definitely pointers needing relocation */
                        dyn->d_un.d_ptr += VDSO_ADDR_ADJUST;
                        break;

                case DT_ENCODING ... OLD_DT_LOOS-1:
                case DT_LOOS ... DT_HIOS-1:
                        /* Tags above DT_ENCODING are pointers if
                           they're even */
                        if (dyn->d_tag >= DT_ENCODING &&
                            (dyn->d_tag & 1) == 0)
                                dyn->d_un.d_ptr += VDSO_ADDR_ADJUST;
                        break;

                case DT_VERDEFNUM:
                case DT_VERNEEDNUM:
                case DT_FLAGS_1:
                case DT_RELACOUNT:
                case DT_RELCOUNT:
                case DT_VALRNGLO ... DT_VALRNGHI:
                        /* definitely not pointers */
                        break;

                case OLD_DT_LOOS ... DT_LOOS-1:
                case DT_HIOS ... DT_VALRNGLO-1:
                default:
                        if (dyn->d_tag > DT_ENCODING)
                                printk(KERN_INFO "VDSO: unexpected DT_tag %x\n",
                                       dyn->d_tag);
                        break;
                }
}

static __init void relocate_vdso(Elf32_Ehdr *ehdr)
{
        Elf32_Phdr *phdr;
        Elf32_Shdr *shdr;
        int i;

        BUG_ON(memcmp(ehdr->e_ident, ELFMAG, 4) != 0 ||
               !elf_check_arch_ia32(ehdr) ||
               ehdr->e_type != ET_DYN);

        ehdr->e_entry += VDSO_ADDR_ADJUST;

        /* rebase phdrs */
        phdr = (void *)ehdr + ehdr->e_phoff;
        for (i = 0; i < ehdr->e_phnum; i++) {
                phdr[i].p_vaddr += VDSO_ADDR_ADJUST;

                /* relocate dynamic stuff */
                if (phdr[i].p_type == PT_DYNAMIC)
                        reloc_dyn(ehdr, phdr[i].p_offset);
        }

        /* rebase sections */
        shdr = (void *)ehdr + ehdr->e_shoff;
        for(i = 0; i < ehdr->e_shnum; i++) {
                if (!(shdr[i].sh_flags & SHF_ALLOC))
                        continue;

                shdr[i].sh_addr += VDSO_ADDR_ADJUST;

                if (shdr[i].sh_type == SHT_SYMTAB ||
                    shdr[i].sh_type == SHT_DYNSYM)
                        reloc_symtab(ehdr, shdr[i].sh_offset,
                                     shdr[i].sh_size);
        }
}

/*
 * These symbols are defined by vdso32.S to mark the bounds
 * of the ELF DSO images included therein.
 */
extern const char vdso32_default_start, vdso32_default_end;
extern const char vdso32_sysenter_start, vdso32_sysenter_end;
static struct page *vdso32_pages[1];

#ifdef CONFIG_X86_64

static int use_sysenter __read_mostly = -1;

#define vdso32_sysenter()       (use_sysenter > 0)

/* May not be __init: called during resume */
void syscall32_cpu_init(void)
{
        if (use_sysenter < 0)
                use_sysenter = (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL);

        /* Load these always in case some future AMD CPU supports
           SYSENTER from compat mode too. */
        checking_wrmsrl(MSR_IA32_SYSENTER_CS, (u64)__KERNEL_CS);
        checking_wrmsrl(MSR_IA32_SYSENTER_ESP, 0ULL);
        checking_wrmsrl(MSR_IA32_SYSENTER_EIP, (u64)ia32_sysenter_target);

        wrmsrl(MSR_CSTAR, ia32_cstar_target);
}

#define compat_uses_vma         1

static inline void map_compat_vdso(int map)
{
}

#else  /* CONFIG_X86_32 */

#define vdso32_sysenter()       (boot_cpu_has(X86_FEATURE_SEP))

void enable_sep_cpu(void)
{
        int cpu = get_cpu();
        struct tss_struct *tss = &per_cpu(init_tss, cpu);

        if (!boot_cpu_has(X86_FEATURE_SEP)) {
                put_cpu();
                return;
        }

        tss->x86_tss.ss1 = __KERNEL_CS;
        tss->x86_tss.sp1 = sizeof(struct tss_struct) + (unsigned long) tss;
        wrmsr(MSR_IA32_SYSENTER_CS, __KERNEL_CS, 0);
        wrmsr(MSR_IA32_SYSENTER_ESP, tss->x86_tss.sp1, 0);
        wrmsr(MSR_IA32_SYSENTER_EIP, (unsigned long) ia32_sysenter_target, 0);
        put_cpu();      
}

static struct vm_area_struct gate_vma;

static int __init gate_vma_init(void)
{
        gate_vma.vm_mm = NULL;
        gate_vma.vm_start = FIXADDR_USER_START;
        gate_vma.vm_end = FIXADDR_USER_END;
        gate_vma.vm_flags = VM_READ | VM_MAYREAD | VM_EXEC | VM_MAYEXEC;
        gate_vma.vm_page_prot = __P101;
        /*
         * Make sure the vDSO gets into every core dump.
         * Dumping its contents makes post-mortem fully interpretable later
         * without matching up the same kernel and hardware config to see
         * what PC values meant.
         */
        gate_vma.vm_flags |= VM_ALWAYSDUMP;
        return 0;
}

#define compat_uses_vma         0

static void map_compat_vdso(int map)
{
        static int vdso_mapped;

        if (map == vdso_mapped)
                return;

        vdso_mapped = map;

        __set_fixmap(FIX_VDSO, page_to_pfn(vdso32_pages[0]) << PAGE_SHIFT,
                     map ? PAGE_READONLY_EXEC : PAGE_NONE);

        /* flush stray tlbs */
        flush_tlb_all();
}

#endif  /* CONFIG_X86_64 */

int __init sysenter_setup(void)
{
        void *syscall_page = (void *)get_zeroed_page(GFP_ATOMIC);
        const void *vsyscall;
        size_t vsyscall_len;

        vdso32_pages[0] = virt_to_page(syscall_page);

#ifdef CONFIG_X86_32
        gate_vma_init();

        printk("Compat vDSO mapped to %08lx.\n", __fix_to_virt(FIX_VDSO));
#endif

        if (!vdso32_sysenter()) {
                vsyscall = &vdso32_default_start;
                vsyscall_len = &vdso32_default_end - &vdso32_default_start;
        } else {
                vsyscall = &vdso32_sysenter_start;
                vsyscall_len = &vdso32_sysenter_end - &vdso32_sysenter_start;
        }

        memcpy(syscall_page, vsyscall, vsyscall_len);
        relocate_vdso(syscall_page);

        return 0;
}

/* Setup a VMA at program startup for the vsyscall page */
int arch_setup_additional_pages(struct linux_binprm *bprm, int exstack)
{
        struct mm_struct *mm = current->mm;
        unsigned long addr;
        int ret = 0;
        bool compat;

        down_write(&mm->mmap_sem);

        /* Test compat mode once here, in case someone
           changes it via sysctl */
        compat = (vdso_enabled == VDSO_COMPAT);

        map_compat_vdso(compat);

        if (compat)
                addr = VDSO_HIGH_BASE;
        else {
                addr = get_unmapped_area(NULL, 0, PAGE_SIZE, 0, 0);
                if (IS_ERR_VALUE(addr)) {
                        ret = addr;
                        goto up_fail;
                }
        }

        if (compat_uses_vma || !compat) {
                /*
                 * MAYWRITE to allow gdb to COW and set breakpoints
                 *
                 * Make sure the vDSO gets into every core dump.
                 * Dumping its contents makes post-mortem fully
                 * interpretable later without matching up the same
                 * kernel and hardware config to see what PC values
                 * meant.
                 */
                ret = install_special_mapping(mm, addr, PAGE_SIZE,
                                              VM_READ|VM_EXEC|
                                              VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC|
                                              VM_ALWAYSDUMP,
                                              vdso32_pages);

                if (ret)
                        goto up_fail;
        }

        current->mm->context.vdso = (void *)addr;
        current_thread_info()->sysenter_return =
                VDSO32_SYMBOL(addr, SYSENTER_RETURN);

  up_fail:
        up_write(&mm->mmap_sem);

        return ret;
}

#ifdef CONFIG_X86_64

__initcall(sysenter_setup);

#ifdef CONFIG_SYSCTL
/* Register vsyscall32 into the ABI table */
#include <linux/sysctl.h>

static ctl_table abi_table2[] = {
        {
                .procname       = "vsyscall32",
                .data           = &sysctl_vsyscall32,
                .maxlen         = sizeof(int),
                .mode           = 0644,
                .proc_handler   = proc_dointvec
        },
        {}
};

static ctl_table abi_root_table2[] = {
        {
                .ctl_name = CTL_ABI,
                .procname = "abi",
                .mode = 0555,
                .child = abi_table2
        },
        {}
};

static __init int ia32_binfmt_init(void)
{
        register_sysctl_table(abi_root_table2);
        return 0;
}
__initcall(ia32_binfmt_init);
#endif

#else  /* CONFIG_X86_32 */

const char *arch_vma_name(struct vm_area_struct *vma)
{
        if (vma->vm_mm && vma->vm_start == (long)vma->vm_mm->context.vdso)
                return "[vdso]";
        return NULL;
}

struct vm_area_struct *get_gate_vma(struct task_struct *tsk)
{
        struct mm_struct *mm = tsk->mm;

        /* Check to see if this task was created in compat vdso mode */
        if (mm && mm->context.vdso == (void *)VDSO_HIGH_BASE)
                return &gate_vma;
        return NULL;
}

int in_gate_area(struct task_struct *task, unsigned long addr)
{
        const struct vm_area_struct *vma = get_gate_vma(task);

        return vma && addr >= vma->vm_start && addr < vma->vm_end;
}

int in_gate_area_no_task(unsigned long addr)
{
        return 0;
}

#endif  /* CONFIG_X86_64 */